Internal combustion engines, especially diesel engines, using water mixed with fuel in the combustion chamber can produce lower NOx, hydrocarbon and particulate emissions per unit of power output. Nitrogen oxides are an environmental issue because they contribute to smog and pollution. Governmental regulation and environmental concerns have driven the need to reduce NOx emissions from engines.
Diesel fueled engines produce NOx due to the relatively high flame temperatures reached during combustion. The reduction of NOx production includes the use of catalytic converters, using “clean” fuels, recirculation of exhaust and engine timing changes. These methods are typically expensive or complicated to be commercially used.
Water is inert toward combustion, but lowers the peak combustion temperature resulting in reduced particulates and NOx formation. When water is added to the fuel it forms an emulsion and these emulsions are generally unstable. Stable water-in-fuel emulsions of small particle size are difficult to reach and maintain. It would be advantageous to make a stable water-in-fuel emulsion that can be made continuously and is stable in storage.
It has been found advantageous to produce stable water-in-fuel emulsions by employing a novel emulsifier that is polyacidic polymer crosslinked with a fuel-soluble dispersant. It would be advantageous to make an emulsifier with improved hydrolytic stability so as to improve the long-term stability of the water in fuel emulsifier.
The term “NOx” is used herein to refer to any of the nitrogen oxides, NO, NO2, N2O, or mixtures of two or more thereof. The terms “aqueous hydrocarbon fuel emulsion” and “water fuel emulsion” are interchangeable. The terms “aqueous hydrocarbon fuel” and “water fuel blend” are interchangeable.